How can i make hollow cylinder but to be closed on top and bottom only hollow inside?
Add a circle mesh.


After that, go into edit mode and extrude it down by selecting all the vertices, pressing E, and then dragging down on the z-axis. Then, select  all the vertices on one side of the cylinder you just made and press F to fill it in, then do the same on the other side. You can use box select to select all the vertices faster (press B and drag out).